Telephone-switchboard.



No. 734,099. PATENTED JULY 21, 1903.

G. E. SGRIBNER.

TELEPHONE SWITGHBOARD;

APPLICATION FILED SEPT. 25, 1896.

NO MODEL.

UNITED STATES Patented July 21, 1903.

PATENT Y OFFICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO WVESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE-SWITCHBOARD.

SPECIFICATION forming part of Letters Patent N 0. 734,099, dated July 21, 1903.

Application filed September 25, 1896. Serial No. 606,926. (No modem To all whom it ntay concern:

Be it known that I, CHARLES E. SCRIBNER, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Supervisory Signals for Telephone-Switchboards, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming'a part of this specification.

My invention relates to automatic signals which are associated with the operators connecting apparatus in a telephone-exchange switchboard; and its object is toprovide an improved organization of circuits and apparatus for the control and operation of such signals. The particular result aimed athas been the-operation of two visible signals in such a manner that the display of either one will always have a single definite meaning for example, one signal may be displayed only upon the establishment of connection with the called line until the response of the called party, While the other will be displayed only to indicate a call for disconnection, as where both subscribers have hung up their telephones at the end of the conversation.

I will describe a telephone-exchange system embodying my invention by reference to the accompanying drawing, which is a diagram illustrating two telephone-lines extending fromsubstations to a central-oflice switchboard, with a set of connecting apparatus for the operator, the system being equipped with signals, which are controlled and operated in the manner which I consider preferable.

The invention is capable of application to different systems and in other forms, and while I shall describe in detail the system shown in the drawing the statement of the general features or combinations which I regard as novel will be reserved for the appended claims.

The-equipment of the subscribers lines is of the well-known type,.the apparatus at the substation comprising the usual signal-bell a,transmitting and receiving telephones ct a and the telephone-switch a controlling the circuit through said telephones. The bell a should have a resistance high in comparison with that of the telephones in order than an appreciable variation of the current in the line may be produced by bringing the telephones into the line-circuit.

The instruments atv stations B and B are of course similar. Line conductors 1 and 2 are led from station B to the switch-springs of the spring-jack c in a switchboard at the central ofiice, and thence through the switchcontacts of the jack, the former to earth through a relay d and the latter to earth through a battery e, which is common to all the lines of the exchange. One of the switchcontacts (l of this relay is connected by wire .3 through the resistance-coilfto earth. The other constitutes the terminal of a conductor 4, which leads through a signal-lamp g, placed near spring-jack c in the switchboard, to the free terminal of the grounded battery 6. There is thus a local circuit 34, which ineludes the resistance-coil f and the lamp g,

which becomes closed when the relay attracts its armature, and thus causes the lighting of lamp g. From the conductor 3, between the contact-piece d and the resistance-coil f, is led a wire 5 to a thimble or ring-contact c of the spring-jack c.

Two plugs 71. and h, of usual construction, are provided each with contact-points i, 2' and i constructed to register with the contact-springs c and c and the ring 0 of the spring-jack. The contacts 6 of the two plugs are united by flexible conductors 6, which include the two windings k and of a repeating-coil k. The other like contacts 2" of the plugs are united through conductor 7, including other windings k and k of the same repeating-coil. The contact-sleeves i of the plugs are connected by conductors 8 and 9 with the free terminal of battery 6. These conductors include resistance-coilsl and Z, respectively. It will be observed that when a plug is inserted in a spring-jack a new circuit is completed through wire 5, thimble 0 contact 2' of the plug, and conductor 8 or 9 to the battery. Thus a shunt is formed about the lamp 9. This shunt should have sufficient resistance-to divert from the lamp such an amount of current that it shall become extinguished. Hence the act of making connection with a line by means of one of the plugs will cause the efiacement of the linesignal controlled by the relay of that line. A branch conductor leads from conductor 6 of the pl ug-circuit intermediate of the windings k to earth. A similar conductor is led from the corresponding pointof conductor 7 of the plug-circuit to the free pole of battery e. The battery e is thus connected in bridge of the plug-circuit between the windings of the repeating-coil to supply current by way of the plug-circuit. to the lines which may be united thereby. The operator is provided with the usual listeningkey m, by which she may connect her telephone 11 into bridge of the plug-circuit, and also with a calling-key 0, which is constructed to disconnect the calling-plug h from its mate and connect its line-contacts with the terminals of a generator of signaling-current when the key is operated. In the operators keyboard (preferably adjacent to the plugs) are placed two signal-lam ps 1* ands. The former of these is to serve as a clearing-out signal and the latter as a ringingsignal to be displayed upon connection with the called line until the called party answers.

In order to utilize the repeating-coil 7t as a relay for controlling signals, I provide for the core of the repeating-coil a pivoted armature k playing between contact anvils It 70 against the former of which the armature lies normally under the influence of a tensionspring. A relay-magnet t, which should be of low resistance, is interposed in conductor 6 of the plug-circuit, between the winding k and the ground connection of the conductor. It is provided with normal and alternate contactanvils t and The armature-lever 70 is connected by a wire 10 with the free pole of a grounded battery u. The continuity of this conductor is controlled by a plug-seat switch 1: in the socket of plug h, being broken at that switch while the plug is idle. The normal resting contact 70 is connected to earth by a wire 11, including lamp-signal r. The alternate contact k of the repeating-coil relay his connected by wire 12 with the lever 25 The normal resting contact of the relayt forms the terminal of a wire 13, which includes the signal-lamp s. The forward contact-anvil t of relay t is connected directly with the conductor 6 between the magnet of the relay and the winding k of the repeating-coil. It may be convenient here to trace the operation in detail of these parts. When the plug h is in its socket, no exciting-current will reach either of the signal-lamps, and the whole apparatus will remain inelfective. When the plug is removed from its socket, the signaling instruments are placed in condition for operation. \Vhen any winding of the repeating-coil is traversed by a current, the core thereof will be excited, and the circuit 10 11, including the signal-lamp 'r and the battery u, will be open at contact 7c ,'and the circuit 10 12 will be closed as far as the armature i and thence through either of two circuits,

according to the position of the armature. \Vhile magnet 25 remains yet unexcited, this latter circuit will be closed to the wire 13, and thence through the lamp 3 to earth. When the current traverses the magnet, this circuit, including the lamp,will be interrupted, and a new circuit will be closed to wire 14. When this last circuit has once been established, the magnet 15 will be constantly excited thereafter by a current through wires 10, 12, and 14 and conductor 6 as long as the armature 70" remains closed to its forward contact. Itwill be observed that in this position of the armature a path for current in conductor 6 exists in shunt of magnet 25 through wires 14, 12, and 10, which is practically of no impedance and, in effect, a short-circuit of the magnet.

I will now pass to the consideration of the operation of this system as a whole. Assume that the subscriber at station E requires connection with substation B. The calling subscriber removes his telephone from its switch, whereby the circuit of battery e is closed from conductor 2 of the line-circuit through the telephones to conductor 1, and thus through the relay d. The relay being excited closes the local circuit 3 4 and lights the individual signal-lamp g. The operator responding to the call inserts plug h in a spring-jack c, at the same time depressing her listening-keym to bring her telephone n into connection with plug-circuit 6 7. The insertion of the plug 71. into the spring-jack brought the circuit, including the resistance-coil Z, into connection with the conductor 5 through the agency of contact i of the plug and c of the spring-jack, wherebya shunt was formed about the lamp 9. A considerable portion of the current in the local circuit was thereby diverted from the lamp g, and the latter was extinguished. The act of inserting the plug in the springjack 0 of the line permitted current to flow from battery c through the windings I0 and 7c of the repeating-coil, and thence through the line-circuit, thus exciting the core of the repeatingcoil and causing it to bring its armature against its forward contact-stop 70 interrupting the circuit to the clearing-out lamp. Having received the order from the calling subscriber in the usual way, the operator inserts the plug h into the spring-jack of line to station 13, signaling to that station by depressing the calling-key 0. The raising of the plug h from the socket-switch permits the latter to close the local battery-circuit including the lamps. Since the relay k is excited, however, the signal r is not lighted thereby. Current finds circuit through wires 10 12 13 and lightslamps. Theinsertion of the plug into the spring-jack of the line called for brings the circuit, including resistancecoil Z, into shunt of the individual signallamp 9 of that line, so that any subsequent excitement of the relay of the called line cannot cause the illumination of the individual lamp. It will be observed that battery e has become connected with the called line through vented by the continued excitement of-the windings k and k of the repeating-coil and by means of conductors 6 and 7 of the plugcircuit, in which the relay i also is included. When the called subscriber, responding to the ringing of his bell, removes his telephone from its switch, a current is created through the conductors of the plug-circuit, the line conductors, and the telephones at the substation, flowing from battery 6 through the winding 10 of the repeating-coil, through a portion of the conductor 7 of the plug-circuit to line conductor 2, thence returning through line conductor 1 and a portion of conductor 6 of the plug-circuit, thence through the winding of the repeating-coil and the relay t to earth. The windings k and k of the repeating-coil are of course in such relation to each other that their magnetizing efiects upon the core are in the same direction. The magnet i being excited, the armature t is drawn forward and closes upon its contact 25 whereby a local circuit is closed made up of wires 14, 12, and 10 and including the battery u, together with magnet if, whereby the excited condition of the magnet is maintained independently of current in the telephone-line, but subject to control by the armature 76 The breaking of connection between wires 12 and 13 when the armature t advances toward its magnet brings about the extinction of ringing-lamp s, which is an indication to the operator that the subscriber called has taken his telephone for use. Communication takes place between the subscribers in the customary way. Current is supplied from battery 6 through the substation-telephones, and variations in the current over each line are produced by variations of the resistance of the transmitting-telephone at the corresponding substation, the telephonic undulations in the current in one line being propagated in the other line through the agency of the repeatingcoil k. If during the continuance of the connection subscriber at station B should replace his telephone on its switch-hook the display of the clearing-out signal will be precore of the repeating-coil by current through the repeating-coil to station B. If the subscriber at the station B should replace his telephone, that at station B being still in use, the lamp 3 would remain unlighted, since relay t has now become connected in a closed battery-circuit comprising conductors 12 and 14 and a portion of conductor 6, as previously traced in describing the action of the relay i when the called subscriber took his telephone for use. It may be noted that the closed branch thus formed from conductor 6 to earth is practically a short-circuit for telephonic currents about the magnet 75, so that the latter constitutes no obstruction in the circuit while the subscribers at the two stations are in communication. When on the termination of conversation both subscribers replace their telephones, thecircuits over both lines are interrupted at the substations, and all the windings of repeating-coil k are deprived of current. Hence the armature of the instrument falls back against its resting contact k ,whereby the local circuit, including the clearing-out signal-lamp r, isclosed and that lamp becomes lighted. The lamp 8 still remains dark, its circuit being open at the relay 7c. The display of the clearing-out signal 1" signifies that conversation has been terminated, Accordingly the operator removes the plugs from their spring-jacks and replaces all the appliances in their normal positions. Thus in this system each signal has a single and definite meaning. The display of the individual line-signal indicates a call, the display of the ringing-signal 8 denotes failure of the called subscriber to respond, while the lighting of the clearing-out signal-lamp 'r' constitutes an instruction to the operator to disconnect the lines.

Having thus described my invention, I desire to secure by Letters Patent 1. The combination with two telephonelines, of a. repeating-coil having a winding in each of the line-circuits,a source of current for said lines, and means at each substation for controlling the current in the line, and an armature for the core of the repeating-coil and a secondary clearing-out signal in a local battery circuit controlled by the armature, whereby the clearing-out signal is displayed only when current has ceased in both telephone-lines, as described.

2. The combination with a telephone-line and a switch at the station thereof for closing the line-circuit in the use of the telephone, a spring-jack for the line and a plug for making connection therewith, a plug-circuit terminating in the plug, a magnet in the plugcircuit responsive to current in the line, and a source of current in a bridge of the plugcircuit, of a normally open shunt of the magnet of slight impedance, and switch-contacts controlled by the magnet adaptedto complete the shunt; whereby theimpedance ofthe magnet is eliminated from the telephone-circuit, as described.

3. The combination with a metallic-circuit telephone-line provided with means for producing a current in the line, of an electromagnet in the line, a normally open shunt about the magnet, a source of current in the shunt and switch-contacts controlled by the magnet adapted to close the shunt when the magnet is excited; substantially as described.

and means for producing current in the line While the telephone is in use, of a magnet in the line-circuit and a signal controlled thereby, being displayed when the magnet is not excited, a normally open conductor adapted to short-circuit the electromagnet, switchcontacts constructed to be closed together when the magnet is excited to complete the said short-circuit, and a source of current in the local circuit formed by the completed short-circuit and the portion of the line-circuit including a magnet, whereby the signalindicator is extinguished and the impedance of the magnet is removed from the circuit when the telephone is brought into use.

6. The combination with two telephonelines, of a repeating-coil having a winding interposed in each of the lines, means for producing current through each of said windings to the corresponding line, and a switch at the substation in each line whose position is changed during the use of the telephone controlling the current in said line, an armature for the repeating-coil and a clearing-out signal displayed thereby in one of its positions, an electromagnet in circuit with the called line and a signal controlled thereby to be displayed when the magnetis inert; as described.

7. The combination with two telephonelines, each provided at a substation with a a switch adapted to close the line-circuit while the telephone is in use, and each connected at a central point with a source of current, of a repeating-coil having a winding in each of the lines, a movable armature for the repeating-coil and a signal-indicator adapted to be displayed by the armature when unattracted, a calling-key in connection with one of the lines, an electromagnet in the same line, a signal controlled by the said magnet to be displayed when the magnet is inert, a local circuit including a winding of the magnet, together with the source of current, and switchcontacts closed by the magnet when excited; substantially as described.

In witness whereof I hereunto subscribe my name this 17th day of July, A. D. 1806.

CHARLES E. SORIBNER. WVitnesses:

ELLA EDLER, MYSTA F. GREEN. 

